1. Field of the Invention
The present invention relates to a chip resistor and a method of making the same.
2. Description of Related Art
An example of conventional chip resistors is illustrated in FIG. 8 of the present application (refer to JP-A-2002-57009). A chip resistor A1 includes a metal chip resistor element 100 which has a lower surface 100a formed with a pair of electrodes 110. Each of the electrodes 110 includes a lower surface formed with a solder layer 120. As understood from the figure, the lower surface 100a of the resistor element includes two areas each covered with the electrode 110 and an exposed area between the electrodes.
In use, the chip resistor A1 is soldered on a printed circuit board for example. It is desirable that molten solder sticks only to the two electrodes 110 of the chip resistor A1. However, according to the conventional structure shown in FIG. 8, molten solder may also stick to the above-described exposed area of the lower surface 100a of the resistor element. If the solder sticks to the lower surface 100a, the chip resistor A1 may exhibit a resistance which is different from an intended resistance, and an electric circuit using the chip resistor A1 may work improperly.
This problem can be solved by covering the above-described exposed area of the lower surface 100a of the resistor element with an insulating film made of resin, for example. However, if the insulating film is not sufficiently adherent to the metal resistor element 100, the insulating film may come off the resistor element 100 due to heat generation from the energized chip resistor A1 (or due to other factors).